DEVELOPMENT OF PALEOBOTANY IN THE ILLINOIS BASIN 3 



known to the new generation of paleobotanists. We have quoted or paraphrased 

 parts of their correspondence and writings to convey something of their insight, 

 their close cooperation, and their friendships, and have recounted some of their 

 experiences that have not been included in more technical accounts . 



Branches of Paleobotany- 

 Paleobotany may be divided into three main specialized areas of study 

 that are largely based on the modes of preservation of the plant parts. An entire 

 plant is rarely found, but even the microscopic forms that are preserved represent 

 a stage or part of a stage in the life history of a plant. Various parts of a plant 

 can be preserved in different environments. 



The branch of paleobotany that was developed first was the study of plants 

 preserved as compressions and impressions. Compressions are the pressed, car- 

 bonized remains of a plant; impressions show the imprint of a plant but lack or- 

 ganic matter. Both are found mainly in shales and lend themselves readily to 

 determinations of the gross morphology of plant organs, particularly foliage. The 

 second branch of paleobotany is the study of plants petrified in calcareous concre- 

 tions called coal balls, which occur in certain coal seams. The actual cell walls 

 of plants are preserved in these nodules, and with special techniques anatomical 

 studies of the fossil plants can be made in many of the same ways that living plants 

 are studied. The third major, and most recently developed, branch of paleobotany 

 is called palynology. It involves the study of plant spores and pollen, which 

 have been preserved in many types of sedimentary rocks, particularly coals. 



The boundaries of the three branches of paleobotany are not always clear 

 cut. For instance, small portions of compressions have been known to grade into 

 petrifactions, and sporangia with spores or pollen are often preserved on compres- 

 sions (Darrah, 1936a; Kosanke, 1955). Thus there is a narrow bridge of compar- 

 able data between the oldest branch of paleobotany and the more recently devel- 

 oped areas of plant anatomy and palynology. 



Peripheral to paleobotany is the science of coal petrography, which yields 

 information on plant structures and the ecology at the time the coal was deposited. 

 As coal petrography is a discipline in its own right, we discuss it only briefly. 



State geological surveys, especially the Illinois State Geological Survey, 

 have been responsible for the initiation and early support of studies in each branch 

 of paleobotany. As was true of past studies, present paleobotanical work is con- 

 cerned mainly with studies in biostratigraphy, plant evolution and ontogeny, and 

 ecological implications of the floras. The biostratigraphic applications of compres- 

 sion-impression floras and the palynology of coals are still, for the most part, the 

 domain of the state geological surveys and geologically oriented paleobotanists. 

 Most studies of coal-ball plants, however, are now being made in botany and bio- 

 logy departments of universities. 



The backgrounds of the paleobotanists are almost as varied as those of 

 the far more numerous amateur collectors and rock hounds who share the same 

 enthusiasm for collecting plant fossils. Until very recently, formal paleobotanical 

 training was available at relatively few universities, most of which are in areas 

 near significant fossil plant deposits, such as the Illinois Basin. Many of us did 

 not become acquainted with paleobotany until relatively late in our college train- 

 ing, and, consequently, many students have followed a rather circuitous path to a 

 career in paleobotany. 



